The Sierra HD is all-new for the ’11 model year and features a redesigned louvered hood, new three-bar grille and full-width front chrome steel bumper.

The redesigned chassis, consisting of 18 all-new fully-boxed high-strength steel frame assemblies, has five times the torsional stiffness than the outgoing model. The front frame structure is also 125% stiffer, and coupled with larger engine and transmission mounts and hydraulic body mounts on extended and crew cab models, greatly improves noise, vibration and harshness characteristics. Towing and payload capacities are also increased.

The front suspension system features redesigned steel upper and precision-machined cast iron lower control arms with five separate torsion bar rates that can be selected depending on intended application and also handles 25% more weight than the outgoing model.

Ride is further improved with an all-new asymmetrical rear leaf spring design that also increases payload capability.

The 6.6L Duramax diesel produces more horsepower and torque than its predecessor while producing 63% fewer oxides of nitrogen (NoX) emissions than the prior model. It also features a new smart exhaust “jake” brake to aid in controlling speed, especially on long downhill grades, extending brake life and preventing overheating. Glow plug cycling times are as low as 3 seconds, even in temperatures up to -20F (-29C) and are best-in-segment, according to GMC.

The Sierra retains the 6.0L V-8 gasoline engine. Both the gasoline and diesel engines are mated to a heavy-duty Allison 6-speed automatic transmission with double-overdrive for more efficient high-speed operation.

The standard 4-wheel anti-lock disc brake system has been recalibrated for improved pedal feel and boasts larger front and rear rotors and stronger calipers than its predecessor.